UPDATED | The Port Authority of New York and New Jersey’s Inspector General formally launched an investigation Tuesday into the closure of several local lanes at the George Washington Bridge in September, which caused major traffic jams. The investigation was confirmed by Michael Nestor, the office’s director of investigations.

And New Jersey state lawmakers are weighing their next step into their investigation into the closures, one day after the Port Authority’s executive director undercut the agency’s official explanation for the traffic jams.

The options for the lawmakers could include new subpoenas for appointees of New Jersey Gov. Chris Christie, who would once again try to explain what happened, this time under oath.

Monday’s sworn testimony from Patrick Foye, the authority’s executive director, contradicted voluntary testimony given to the New Jersey Assembly Transportation Committee by another authority official on a key point: whether a traffic study was really the reason lanes were abruptly shifted on the world’s busiest bridge.

Bill Baroni, the deputy executive director and a top appointee of Mr. Christie, had doubled down on that explanation in an appearance before the committee last month. Mr. Baroni said then that David Wildstein, his subordinate and another official with close ties to the governor, gave the order to close two of three local access lanes from Fort Lee, N.J., onto the bridge so the authority could make a decision about the fairness of dedicating toll plaza lanes to local traffic.

But people familiar with the matter had long cast doubt on that explanation, and on Monday Mr. Foye, the top appointee of Gov. Andrew Cuomo, said it wasn’t true.

“I’m not aware of any traffic study,” Mr. Foye told the committee. “I don’t know why it was done.”

Democratic lawmakers have suggested the lane closures were a gesture aimed at Fort Lee, which was beset by traffic due to the lane closures, and where the borough’s Democratic mayor had declined to endorse Mr. Christie’s reelection. A Christie spokesman has called that notion “crazy.”

One day after the hearing, the incident received new national attention. Fresh off an appearance on Rachel Maddow’s MSNBC show to discuss the matter, Assemblyman John Wisniewski said he was “not ruling anything out and not ruling anything in.” Mr. Wisniewski is chairman of the transportation committee, and a former chairman of the state Democratic Party who has tangled with the Christie administration and the authority.

Mr. Wisniewski said he wants to “take a look at the transcripts from both hearings and figure out where the holes are in the testimony, and what jumps out from those gaps.”

“I’ve got to be honest with you there’s something wrong with this story,” Mr. Wisniewski said. “That’s something that speaks to an institutional problem at the Port Authority.”

Mr. Wildstein resigned last week, effective Jan. 1, and Mr. Wisniewski and Democratic colleagues have said Mr. Baroni too should resign. Also on Tuesday, New York State Senator Adriano Espaillat and New York State Assemblywoman Gabriela Rosa said that Mr. Baroni should resign.

A spokesman for Mr. Christie didn’t respond when asked if the governor was confident in the accuracy of Mr. Baroni’s testimony, or whether he believed Mr. Baroni should consider resigning.

Messrs. Baroni, Wildstein, and Foye didn’t respond to requests for comment relayed by an authority press officer on Tuesday.